The study of the interaction of mud-flows with obstacles is important to define inundation zones in urban areas and to design the possible structural countermeasures. The paper numerically investigates the impact of a...The study of the interaction of mud-flows with obstacles is important to define inundation zones in urban areas and to design the possible structural countermeasures. The paper numerically investigates the impact of a mud-flow on rigid obstacles to evaluate the force acting on them using two different depth-integrated theoretical models, Single-Phase Model(SPM) and Two-Phase Model(TPM), to compare their performance and limits. In the first one the water-sediment mixture is represented as a homogeneous continuum described by a shearthinning power-law rheology. Alternatively, the twophase model proposed by Di Cristo et al in 2016 is used, which separately accounts for the liquid and solid phases. The considered test cases are represented by a 1D landslide flowing on a steep slope impacting on a rigid wall and a 2D mud dam-break flowing on a horizontal bottom in presence of single and multiple rigid obstacles. In the 1D test case, characterized by a very steep slope, the Two-Phase Model predicts the separation between the two phases with a significant longitudinal variation of the solid concentration. In this case the results indicate appreciable differences between the two models in the estimation of both the wave celerity and the magnitude of the impact, with an overestimation of the peak force when using the Single-Phase Model. In the 2D test-cases, where the liquid and solid phases remain mixed, even if the flow fields predicted by the two models present some differences, the essential features of the interaction with the obstacles, along with the maximum impact force, are comparable.展开更多
This study is devoted to the interaction between water surface waves and a thin layer of viscoelastie mud on the bottom. On the assumption that the mud layer is comparable in thickness with the wave boundary layer and...This study is devoted to the interaction between water surface waves and a thin layer of viscoelastie mud on the bottom. On the assumption that the mud layer is comparable in thickness with the wave boundary layer and is much smaller than the wavelength, a two-layer Stokes boundary layer model is adopted to determine the mud motions under the waves. Analytical expressions are derived for the near-bettom water and mud velocity fields, surface wave-damping rate, and interface wave amplitude and phase lag. Examined in particular is how these kinematic quantities may depend on the viscous and elastic properties of the mud.展开更多
The 2008-05-12 Wenchuan mud-volcano-earthquake was accompanied with eruption of a huge volume of gas and stone,revealing that earthquakes generally result from instant reverse phase explosion of supercritical water(SC...The 2008-05-12 Wenchuan mud-volcano-earthquake was accompanied with eruption of a huge volume of gas and stone,revealing that earthquakes generally result from instant reverse phase explosion of supercritical water(SCW) at the supercritical point.In the deep parts of the crust and mantle there still exists a large amount of supercritical water equivalent in order of magnitude to that of the Earth's hydrosphere.Soft fluids which exist in the MOHO at the top of the upper mantle are the so-called deep supercritical fluids(SCWD).Supercritical water(SCW) has n×103 times strong capability to dissolve gas.Its viscosity is extremely low and its diffusivity is extremely strong.Therefore,it can naturally migrate toward a region with relatively negative pressure.In the steep break zone of the MOHO at the 57-65 km depth beneath the earthquake belt,due to mutation of overburden pressure,SCWD can automatically separate out CaSiO3 and other inorganic salts,evolving into the SCW(H2O-CO2-CH4O system.In going upwards to the 10-20-km depth of the crust SCW will be accumulated as an earthquake-pregnant reservoir in the broken terrain.The phase-transition heat of SCW is estimated at 606.62 kJ/kg and the reverse phasing kinetic energy is 2350.8 kJ/kg.When automatic exhaust at the time of decompression reaches the critical pressure(Pc),the instant explosion reverse phase will be normal-state air water.It will release a huge volume of energy and high-kinetic-energy gas which has been expanded by a factor of 1000,leading to the breaking of the country rocks overlying the earthquake-pregnant reservoir,thus giving rise to a Ms 8.0 earthquake.As a result,there were formed eruptive and air-driven(pneumatic) debris flows whose volumatric flow rate reaches n×1014 m3/s,and their force greatly exceeds the power of INT explosive of the same equivalent value.展开更多
基金the framework of the project MISALVA,financed by the Italian Minister of the Environment,Land Protection and Sea.CUP H36C18000970005
文摘The study of the interaction of mud-flows with obstacles is important to define inundation zones in urban areas and to design the possible structural countermeasures. The paper numerically investigates the impact of a mud-flow on rigid obstacles to evaluate the force acting on them using two different depth-integrated theoretical models, Single-Phase Model(SPM) and Two-Phase Model(TPM), to compare their performance and limits. In the first one the water-sediment mixture is represented as a homogeneous continuum described by a shearthinning power-law rheology. Alternatively, the twophase model proposed by Di Cristo et al in 2016 is used, which separately accounts for the liquid and solid phases. The considered test cases are represented by a 1D landslide flowing on a steep slope impacting on a rigid wall and a 2D mud dam-break flowing on a horizontal bottom in presence of single and multiple rigid obstacles. In the 1D test case, characterized by a very steep slope, the Two-Phase Model predicts the separation between the two phases with a significant longitudinal variation of the solid concentration. In this case the results indicate appreciable differences between the two models in the estimation of both the wave celerity and the magnitude of the impact, with an overestimation of the peak force when using the Single-Phase Model. In the 2D test-cases, where the liquid and solid phases remain mixed, even if the flow fields predicted by the two models present some differences, the essential features of the interaction with the obstacles, along with the maximum impact force, are comparable.
基金The work was supported by the Research Grants Council of the Hong Kong Special Administrative Region, China ,through Project Nos . HKU7081/02Eand HKU7199/03E.
文摘This study is devoted to the interaction between water surface waves and a thin layer of viscoelastie mud on the bottom. On the assumption that the mud layer is comparable in thickness with the wave boundary layer and is much smaller than the wavelength, a two-layer Stokes boundary layer model is adopted to determine the mud motions under the waves. Analytical expressions are derived for the near-bettom water and mud velocity fields, surface wave-damping rate, and interface wave amplitude and phase lag. Examined in particular is how these kinematic quantities may depend on the viscous and elastic properties of the mud.
文摘The 2008-05-12 Wenchuan mud-volcano-earthquake was accompanied with eruption of a huge volume of gas and stone,revealing that earthquakes generally result from instant reverse phase explosion of supercritical water(SCW) at the supercritical point.In the deep parts of the crust and mantle there still exists a large amount of supercritical water equivalent in order of magnitude to that of the Earth's hydrosphere.Soft fluids which exist in the MOHO at the top of the upper mantle are the so-called deep supercritical fluids(SCWD).Supercritical water(SCW) has n×103 times strong capability to dissolve gas.Its viscosity is extremely low and its diffusivity is extremely strong.Therefore,it can naturally migrate toward a region with relatively negative pressure.In the steep break zone of the MOHO at the 57-65 km depth beneath the earthquake belt,due to mutation of overburden pressure,SCWD can automatically separate out CaSiO3 and other inorganic salts,evolving into the SCW(H2O-CO2-CH4O system.In going upwards to the 10-20-km depth of the crust SCW will be accumulated as an earthquake-pregnant reservoir in the broken terrain.The phase-transition heat of SCW is estimated at 606.62 kJ/kg and the reverse phasing kinetic energy is 2350.8 kJ/kg.When automatic exhaust at the time of decompression reaches the critical pressure(Pc),the instant explosion reverse phase will be normal-state air water.It will release a huge volume of energy and high-kinetic-energy gas which has been expanded by a factor of 1000,leading to the breaking of the country rocks overlying the earthquake-pregnant reservoir,thus giving rise to a Ms 8.0 earthquake.As a result,there were formed eruptive and air-driven(pneumatic) debris flows whose volumatric flow rate reaches n×1014 m3/s,and their force greatly exceeds the power of INT explosive of the same equivalent value.
